brief note on input device
Answers
In computing, an input device is a piece of computer hardware equipment used to provide data and control signals to an information processing system such as a computer or information appliance. Examples of input devices include keyboards, mouse, scanners, digital cameras and joysticks. Audio input devices may be used for purposes including speech recognition. Many companies are utilizing speech recognition to help assist users to use their device(s).
Computing
modality of input (e.g. mechanical motion, audio, visual, etc.)
whether the input is discrete (e.g. pressing of key) or continuous (e.g. a mouse's position, though digitized into a discrete quantity, is fast enough to be considered continuous)
the number of degrees of freedom involved (e.g. two-dimensional traditional mice, or three-dimensional navigators designed for CAD applications)